1. Field of the Invention
The present invention relates generally to reed switches and more specifically to the method of using one or more reed switches to control one or more devices.
2. Description of the Related Art
Reed switches are magnetically-operated switches, which are generally formed by a pair of spaced ferromagnetic contacts or blades, hermetically sealed in a glass capsule. In a typical application and use of a reed switch, the blades are connected to outside leads—each outside lead being part of a circuit. The exposure of the blades to a magnetic field—coming from either a permanent magnetic or electromagnetic generation—forces the blades to move, either contacting one another or moving away from one another. In what is known as a normally closed reed switch (“Normal” in this sense and as will be used herein means a state where the reed switch is exposed to a magnetic field), the blades touch when exposed to a magnetic field. By removing the magnetic field, the normally closed reed switch opens and the contacts will no longer touch. Contrariwise, in a normally open reed switch, the contacts touch in the absence of a magnet. By exposing the normally open reed switch to the magnetic field, the contacts move apart and the circuit is opened. After the magnetic field has been removed from these reed switches, the blades will return to their original position.
Generally, the reed switch is activated (that is, causing the ferromagnetic blade to move, be it closing the circuit or opening the circuit) via the use of a magnetic field. Such an activation allows communication to be established with a system or device. In some instances the communication may be the lack of a signal or electrical energy being returned when the switch opens the circuit, while in other instances, the communication may be the circuit being completed. One recognized use of a reed switch is monitoring the “change of state” of something in security systems. For example, a reed switch can cause a circuit to be completed or broken when a window or door opens or closes. This change of condition (opening or closing of the circuit) can automatically be detected by a central alarm system or the like, indicating whether or not an unauthorized “change of state” has occurred. A typical security use of such a reed switch may be, for example, on a window or door of a house or on a roll-up door of a storage shed. In such situations, it is well known and understood that the central alarm system receives a low voltage signal passing through the reed switch to indicate one status of the door or window, and does not receive the low voltage signal from the open reed switch when the door or window is in another state.
With the use of reed switches to control a device, several design considerations must be taken into account. Reed switches are by their very nature fragile—that is, the glass capsules can break. An exacerbation of the fragile nature is the likelihood that two reed switches in too close proximity to one another may hit and break each other.